I reckon the guys at Freshfields Market in Croydon would be worth an ask.
They give a 10% discount on all bottles and cask beers anyway if you’ve got a Camra card or you get six bottles and they are friendly and approachable. They’re carry outs from Sanderstead are ridiculously cheap too.
They run the Croydon craft beer fesitival.
I’m pretty sure you’d be able to strike a deal with them. They have their own beer delivery club too.